If asdf-vm was installed with a package manager and the user doesn't
have the necessary permissions to update it with `asdf update`, asdf-vm
emits an informational message and exits with exit code 1.
This makes it hard to programmatically detect whether the update failed
or wasn't even attempted because it's not possible.
With this change, asdf-vm would exit with the exit code 42 if updates are
disabled instead of exit code 1, which signals an error during update.
Refs r-darwish/topgrade#367
